zahndok

Showing my complete ignorance here, but can someone explain what a Flat Tappet cam is and how it relates to hydraulic, roller, solid? I have a 575sci that I understand has a flat tappet cam.

formula31

Well, no expert by an means, but.

Flat tappet solid. Strong cam with high lift rates and capable of high rpms. Lifters are basically a chunk of steel that directly transfer the cam motion to the valves. Requires adjustment and can be noisy. Correct break in required.

Flat tappet hydraulic. Old school but very reliable IF broken in correctly. Arguably the best reliability and least maintenance. Limited in lift rates and max lift.

Roller Hydraulic. Fast lift rates, no worry about break in. 30 more hp possible due to fast lift rates. Lifters subject to failure due to rollers and cross links. Newer ones probably better in reliability.

Roller solid. Same as above but even more HP gains available. Still has the downside of needing periodic adjustment like the solid flat tappet. More for high rpm applications.

Crazyhorse

Formula31, in a nut shell, has it right. Now here are a few pieces of trivia to really bake your noodle;
All lifters translate rotary movement into vertical movement.
"Flat-tappet" lifters aren't really flat, as they have a slight crown on the bottom.
Hydraulic and solid lifters, whether they are roller or flat-tappet, have oil flowing through them so that oil can get up the pushrods to the rocker arms. Unless you have a Chrysler, in which case you won't be able to buy a friend here.
They all go bad, sooner or later. Just some go sooner rather than later.
They all perform well, as long as you use them in their proper application.
Water is not a good lubricating liquid and is not your friend in an oiling system. Neither is anti-freeze.
F-31, did I miss anything? I mean besides not smoking dope while assembling an engine,,,,,

formula31

Thanks Dave. Yea, there is lots more really. If you have an exhaust sytem that allows you to remove the valve covers without removing the exhaust, and you want max HP and RPM, and you like to play with the motors, go solid. If you are like 95% of the rest of us, who cant get at the valve train and dont want too unless forced, go hydraulic.

formula31

And if you have the money, go hydraulic roller for the extra "free" horsepower. Have the mark 4 block liter bores checked carefully for perpendicularity before doing so.. They may have to be bored and sleeved.

Crazyhorse

jeez, them big words gimme a headache.

formula31

Whats more amazing is that I speelled it right the first time.

Crazyhorse

I'm surprised one has mentioned mushroom lifters, even though they aren't used in any current automotive or marine applications that I know of. The old Ford flat-heads had them, as well as some forties-fifties high-lift cam designs. Recip aircraft engines still use them.

zahndok

Thanks for the edumacation and Merry Christmas to all.

Reed Jensen

Also... a camshaft that pushes flat tappets has more abrupt ramp angles and a pointy lobe. This is because the tappet gives the valve a certain amount of "dwell" while open . Whereas the roller contact with the cam is minimal compared to the flat tappet.. so... the lobe on the cam has a pronounced "dwell" area on the lobe itself. If you saw the two different styles next to each other... it would make sense.